The action takes place in XV century. Iolanta, the blind daughter of the King
of Provence, is whiling away the time in the gar­den of the castle. As the
curtain rises she is talk­ing to her nurse, Marta. She tells Marta that she
has never ever felt so depressed, Iolanta’s friends, Brigitte and Laura, try to
cheer her up by singing songs and bringing her posies of flowers. Marta also
tries to comfort Iolanta by singing her favourite lullaby. This sends Iolanta to
sleep. The sleeping Iolanta is carried into the castle. There is a fanfare of
trumpets and Almerik, King Rene’s sword-bearer, appears. He informs the castle
doorman, Bertrand, that very soon the King will be arriving with a famous
Physician who, it is hoped, will cure Iolanta of her blindness. The trumpets
sound again, announcing the arrival of the King. King Rene enters accompanied by
the Moorish Physician, Ibn-Hakia. King Rene tells Ibn-Hakia that Iolanta has
been betrothed from infancy to Robert, Duke of Burgundy, and is soon to marry
him, but the Duke does not know that his future wife is blind and, indeed,
Iolanta herself is totally unaware of her misfortune, Iolanta had been brought
up by her father in this remote cas­tle and he had surrounded her with loyal
retain­ers whom he had ordered on pain of death not to tell her the truth.
Ibn-Hakia says that the only cure for Iolanta is to inform her of her disability
and then, so long as she passionately wishes to recover her sight, she will do
so. King Rene, full of anxieties for his daughter, retires in indecision to the
castle together with the Physician.

Robert, Duke of Burgundy, and his friend the Knight, Count Vaudemont, appear
on the scene. They are impressed to find a beautiful garden in such a wild,
remote spot. The notice over the entrance to the garden which threatens with
death anyone entering it without permission, puz­zles them. Robert is
downhearted for he is soon to be united in matrimony with Iolanta whom he has
never met and his heart already belongs to another, Iolanta appears on the
castle terrace. Vaudemont is struck by her beauty. Hearing voic­es, she does
not recognize, Iolanta suggests to the strangers that they rest under the shade
of the trees and she hurries off to fetch them some wine. Left alone with his
friend, the Duke, who has a sceptical attitude to the world, voices his
apprehensions and decides to leave; Vaudemont, who is quite enchanted by
Iolanta’s beauty, stays behind. When Iolanta returns he tells her of the great
impression she has made on him and asks her to pick him a red rose in
mem­ory of their meeting, Iolanta plucks him a rose, but it is a white one.
Vaudemont repeats his request and again he is handed a white rose. The Count
begins to suspect something is wrong. He picks a bunch of roses and asks Iolanta
to tell him how many flowers there are in the bunch, Iolanta asks him to give
her the roses so that she may count them. Vaudemont now realizes that Iolanta is
blind. And he tells her so. He tries, in so far as is possible, to comfort
Iolanta but, getting somewhat carried away, he starts to describe to her the
beauties of God’s world which she is destined never to see.

Voices are heard: the King enters, followed by Physician Ibn-Hakia and
servants. Rene is horrified when he learns that Vaudemont has told Iolanta of
her disability; he does not know what to do to help his daughter and eventually
suggests that she should try Physician Ibn-Hakia’s course of treatment, Iolanta
is not enthusiastic about this and says she is quite happy as she is which makes
the Physician lose all hope that his treatment will be effective. Noticing that
Iolanta is very much taken by Vaudemont, King Rene tells the Knight that he will
be executed unless his daughter recov­ers her sight, Iolanta, out of her
mind with love for Vaudemont, begs the Physician to cure her and goes with him
into the castle.

A fanfare of trumpets announces the arrival of the Duke of Burgundy who, with
a group of armed knights, is hurrying to the rescue of his friend. Robert is
amazed to see King Rene. Vaudemont confesses to Robert that he is in love with
Iolanta, the latter’s betrothed, and asks him to tell the King that he, Robert,
has given his heart to someone else. Rene consents to the marriage of Iolanta
and Count Vaudemont. Shouts of joy are heard, Iolanta, who has recov­ered
her sight, appears at the castle door. Overjoyed, King Rene hurries to embrace
his daughter and then leads Vaudemont up to her. Falling on her knees, Iolanta
gives passionate thanks to God for her recovery.